1. Field of the Invention
The present application relates to an anti-fingerprint coating material. More particularly, the present application relates to a non-fluorinated coating materials with anti-fingerprint property, as well as a method for manufacturing thereof, and evaluating anti-fingerprint properties of the coating material.
2. Description of Related Art
For the electronic products with touch screen displays, such as game consoles, smart phones and tablet computers, the touch screens are operated by the touch of a finger. However, the fingerprint problem on the touch screen surface is a serious concern, which is usually addressed by the usage of protective coating materials.
The protective coating materials used to keep the electronic products surface clean should have a property which resist to both water and oil, since the fingerprint problem is caused by the sweat and sebum transferred from the users fingers. To aim to the clear appearance of the electronic products, a variety of approaches to develop a protective coating material has been revealed through the prior arts.
It is suggested that there are two factors contribute to the hydrophobic and oleophobic properties on surfaces: chemical composition and topography (roughness). To address the hydrophobic and oleophobic properties, the commonly used method is to modify the surface by using perfluoroalkyl-based compounds to impart the hydrophobic and oleophobic properties on surfaces. Besides, silica particles existed in the surface modification composition have also been used to create roughness, making the surface hydrophobic. Separately, the colloidal silica nanoparticles with fluoroalkylsilane have been mounted on the glass surface to construct siloxane film with super repellency for liquids. In addition, hybrid films consisting of fluoropolymer and silica particles have been fabricated to generate strawberry-like or quincunx-shaped composite silica particles on glass surfaces for achieving hydrophobic properties.
Although fluorinated compounds are guaranteed as a most favorable chemical to assure anti-fingerprint property, the high cost and environment risks cannot be passed over. In order to avoid environmental pollution, a variety of coating materials have been taught in prior art.
U.S. Pat. No. 2008/0131706 discloses a polysilazane-based composition as a permanent anti-fingerprint coating. The composition contains no chromium; therefore environmental pollution problems are avoided. However, the organic resin is highly specific and therefore difficult to produce. In addition, the composition is only used for application to a metal surface.
U.S. Pat. No. 2006/0110537 discloses an anti-fingerprint coating construction which has anti-corrosion, anti-dust, and anti-fingerprint characteristics. When the coating construction is employed on a surface, sweat on users' fingers is not liable to be adhered to the surface. Besides, the coating construction contains no chromium and doesn't need to process by an acid or alkali solution. This makes the coating construction environmentally friendly. Although this coating construction is with great properties, this trail is aim to an eco-friendly coating material without causing heavy metal pollution.
It is an object of the present invention to provide an anti-fingerprint coating material which is halogen free. Furthermore, the anti-fingerprint coating of the present invention produced from a manufacture process without eco-risk conditions, such as UV-light or high temperature treatment.
In the context of the present invention, the anti-fingerprint coating material is fabricated through simple and popular self-assembly method. It is known that the driving force for the self-assembly is the in-situ formation of polysiloxane, which is connected to surface silanol group (—SiOH) via Si—O—Si bonds. The self-assembling molecules consist generally of three parts: the head group, the alkyl chain and the terminal end group. The head group, i.e., trichloro-, trimethoxy- or triethoxysilane, is responsible for the anchoring of the molecules onto the substrate. The alkyl chain provides the stability of the monolayer; the terminal end group introduces chemical functionality into the monolayer system. The head group of the self-assembling molecules form the Si—O—Si bond through nucleophilic substitution which can occur in organic compounds that have an electronegative atom or group bonded to a sp3 hybridized carbon. And since halogens are more electronegative than carbon, so they have a larger share of the electrons. This polar C-halogen bond causes the head group of the self-assembling molecules to undergo substitution reactions. Since the electronegativity of C-halogen facilities the SiOH surface binding, more precise control of the reaction conditions is needed for organosiliane SAM to make self molecular assemble.
High quality self-assembly monolayers (SAM) are not easy to acquire, because of the need to carefully control the amount of water in solution. As understood, incomplete monolayers are form in the absence of water, excess water results in facile polymerization in solution and polysiloxane deposition of the surface. Depending on the water content of the silane solution, two types of SAM growth behavior has been observed: homogeneous growth and island-type growth (Valiant et al.). As observation, the more water content existed in the SAM reaction environment, the more pre-organized aggregation of siloxanes is formed. The island-type growth SAM can make the coated surface bumpy, and expectedly the surface roughness can be adjusted by control the water content in the reaction environment.
Temperature has been found to play an important role in monolayer formation. Different temperatures can cause the different reactions of hydrolyzed reactive group (such as trichlorosilyl) with the other reactive group in solution or with the other reactive group in the Si—OH surface. Moreover, the influence of the other parameters such as solvent, solution age, terminal function group, alkyl chain length, surface Si—OH group concentration, deposition time are also reported (Wasserman et al., 1989; Silberzan et al., 1991; Grange at al., 1993; Rye, 1997; Sagiv, 2009).
Besides the anti-fingerprint coating materials, the applicant also finds that the traditional evaluating method for anti-fingerprint surface properties is not enough. Since the chemical constituent of human's fingerprint is mainly composed of water and oleic acid and its derivatives. Using water drop test to examine the hydrophobic surface property does not represent anti-fingerprint properties. Therefore, in the present application, a systemic method for evaluating surface properties of a surface of a glass substrate is provided.